This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to Japanese Application No. 2000-346450 filed on Nov. 14, 2000, the entire content of which is incorporated herein by reference.
The present invention generally relates to a solenoid valve. More particularly, the present invention pertains to a damper mechanism of a movable member included in a solenoid valve having a valve mechanism portion which opens and closes in accordance with the movement of the movable member in the axial direction for establishing and interrupting the fluid communication.
Known solenoid valves have a valve mechanism which opens and closes in accordance with the movement of the movable member in the axial direction for establishing and interrupting fluid communication. These solenoid valves also include a damper mechanism for slowing the moving speed of the movable member in the axial direction for purposes of reducing the noise generated when the solenoid valve is opened and closed.
Japanese Patent Laid-Open Publication No. H08-93955 and Japanese Patent Laid-Open Publication No. H09-502947 disclose a solenoid valve which includes a movable member disposed in a sleeve in an axially slidable manner, a valve mechanism for establishing and interrupting the fluid communication through opening and closing of the valve in accordance with the movement of the movable member in the axial direction, a valve chamber exposed to an end surface of the movable member at a valve mechanism portion side and to the valve mechanism portion, and a damper chamber exposed to the opposite end surface of the moveable member. A ring groove is provided on the external surface of the movable member. The valve chamber and the damper chamber are sealed in a liquid-tight manner by the cooperation of a seal ring provided in the ring groove and an internal surface of the sleeve. The communication between the valve chamber and the damper chamber is established through a communication bore provided in the movable member. The operational fluid in the damper chamber is introduced into the valve chamber via the communication bore. With the solenoid valve constructed in the manner described above, because the operational fluid in the damper chamber is introduced into or discharged from the valve chamber via the communication bore in accordance with the movement of the movable member when the movable member is actuated, the moving speed of the movable member in the axial direction is slowed by a differential pressure generated when the operational fluid passes through the communication bore. As explained above, the damper mechanism of the movable member is structured with the seal ring and the communication bore in the known solenoid valve.
However, with this construction of the known solenoid valves, the seal ring is required for providing the damper mechanism of the movable member. Further, in order to receive the seal ring, the ring groove has to be machined on the external surface of the movable member. This increases the overall cost for the solenoid valve in terms of the number of parts and the manufacturing cost.
A need thus exists for a solenoid valve which has a movable member with damper effects, but which is not as susceptible to the drawbacks mentioned above.
In accordance with one aspect of the invention, a solenoid valve includes a sleeve, a movable member disposed in the sleeve to move in an axial direction, a valve mechanism portion that is openable and closable in accordance with axial movement of the movable member for establishing and interrupting operational fluid communication across the valve mechanism portion, a valve chamber exposed to the valve mechanism portion and an end surface of the movable member at a valve mechanism portion side of the movable member, and a damper chamber exposed to an axially opposite end surface of the movable member located opposite the end surface at the valve mechanism portion side. A throttling portion is unitarily formed on a sliding surface of the movable member to establish fluid communication between the damper chamber and the valve chamber and introduce operational fluid from the damper chamber to the valve chamber.
According to another aspect of the invention, a solenoid valve for controlling fluid flow between an inlet and an outlet includes a sleeve, an axially movable member disposed in the sleeve and having a first end surface at one axial end of the axially movable member and a second end surface at an axially opposite end of the axially movable member, a solenoid coil positioned adjacent the sleeve and adapted to be energized to axially move the axially movable member, a valve mechanism portion openable and closable in response to axial movement of the axially movable member for respectively permitting and preventing fluid communication between the inlet and the outlet, a valve chamber exposed to the valve mechanism portion and to the first end surface of the axially movable member, and a damper chamber exposed to the second end surface of the axially movable member. At least one recess is formed in the axially movable member and constitutes a throttling portion establishing fluid communication between the damper chamber and the valve chamber.